查看下面的代码。我想将USERNAME
替换为参数field
中收到的字段名称。此方法必须能够在多个字段上进行搜索。
感谢,
public void Searching(string field, string stringToSearch)
{
var res =
from user in _dataContext.USERs where
user.USERNAME.Contains(stringToSearch)
select new
{
Id = user.ID,
Username = user.USERNAME
};
}
答案 0 :(得分:15)
您需要忘记匿名类型,可以使用Tuple<int,string>
代替;但是:怎么样:
IQueryable<Foo> source = // YOUR SOURCE HERE
// in-memory dummy example:
// source = new[] {
// new Foo {Id = 1, Bar = "abc"},
// new Foo {Id = 2, Bar = "def"}
// }.AsQueryable();
string field = "Bar";
string stringToSearch = "d";
var param = Expression.Parameter(typeof (Foo), "x");
var predicate = Expression.Lambda<Func<Foo, bool>>(
Expression.Call(
Expression.PropertyOrField(param, field),
"Contains", null, Expression.Constant(stringToSearch)
), param);
var projection = Expression.Lambda<Func<Foo, Tuple<int, string>>>(
Expression.Call(typeof(Tuple), "Create", new[] {typeof(int), typeof(string)},
Expression.PropertyOrField(param, "Id"),
Expression.PropertyOrField(param, field)), param);
Tuple<int,string>[] data = source.Where(predicate).Select(projection).ToArray();
答案 1 :(得分:4)
事实上,可以使用Expression API:
public void Searching(Expression<Func<User,string>> field, string stringToSearch)
{
var call = Expression.Call(field.Body, typeof (string).GetMethod("Contains"), new[] {Expression.Constant(value)});
Expression<Func<User, bool>> exp = Expression.Lambda<Func<User, bool>>(Expression.Equal(call, Expression.Constant(true)), field.Parameters);
var res = _dataContext.USERs.Where(exp).Select(u=>new { id= u.ID, Username = u.USERNAME});
}
答案 2 :(得分:3)
你正在尝试的是不可能的。但是,您可以使用dynamic linq library来实现您想要的目标